I. Field of the Invention
The present invention relates to a cryogenic storage device.
II. Description of the Prior Art
There are a number of previously known cryogenic storage devices for storing sperm specimens, tissue cultures and the like. The previously known storage units typically comprise a housing in which a cryogenic storage tank is contained. Plumbing is attached directly to the housing for connecting the fill line of the cryogenic storage tank to an external source of coolant, typically liquid nitrogen. Thus, whenever the level of the nitrogen in the storage tank falls below a predetermined amount, the circuitry opens the valve between the external coolant source and the fill line of the storage tank thus filling the storage tank in the desired fashion.
These previously known storage tanks, however, have suffered from a number of disadvantages. One disadvantage of these previously known storage tanks is that such storage tanks are very difficult to repair and maintain. For example, in the event of failure of one of the components of the storage tank, for example the electronic circuitry or the plumbing components, it is necessary to ship the entire housing, and oftentimes the crygenic storage tank, back to the factory. This is very expensive since such housings are typically three or four feet tall, several feet wide and several feet deep.
A still further disadvantage of these previously known cryogenic storage devices is that, when the lid of the storage tank is opened, nitrogen vapors create a fog at the top of the storage tank. These nitrogen vapors obscure the vision of the operator when inserting specimens into or removing specimens from the cryogenic storage tank.